JP6017818B2 - Lighting device and lighting device - Google Patents

Description

  The present invention relates to a lighting device and a lighting device. The present invention particularly relates to an LED lighting device.

  2. Description of the Related Art Conventionally, there is a lighting device including an electrolytic capacitor and a lighting circuit unit that inputs a direct current obtained by the electrolytic capacitor and outputs an output current of a predetermined target current amount to a light source (see, for example, Patent Document 1). . The electrolytic capacitor is provided on the output side of the boost chopper circuit, for example. The lighting circuit unit is, for example, a buck converter circuit, and a MOSFET is provided on the input side thereof.

JP 2012-15052 A

  It is known that an electrolytic capacitor causes a decrease in capacity due to freezing of the internal electrolyte at low temperatures. When the lighting device provided with the boost chopper circuit and the buck converter circuit described above is used at a low temperature of −40 ° C., the capacitance of the electrolytic capacitor of the boost chopper circuit is reduced, so that the MOSFET of the buck converter circuit The reverse voltage was applied to the MOSFET, and there was a problem that the MOSFET might break down.

  An object of the present invention is to prevent a reverse current from flowing through a switching element of a lighting circuit even when the lighting device is used at a low temperature such as −40 ° C., for example.

A lighting device according to one aspect of the present invention includes:
An electrolytic capacitor that smoothes the input voltage and outputs a DC voltage;
A switching element that performs a switching operation by a DC voltage output from the electrolytic capacitor, and a lighting circuit that outputs a predetermined DC current by the switching operation of the switching element to light a light source;
A rectifier that controls the direction of the current flowing through the switching element of the lighting circuit in one direction from the electrolytic capacitor side to the light source side.

  In one aspect of the present invention, the rectifying unit of the lighting device controls the direction of the current flowing through the switching element of the lighting circuit in one direction from the electrolytic capacitor side to the light source side, so that the lighting is performed at a low temperature of −40 ° C. Even if the device is used, no reverse current flows through the switching element of the lighting circuit.

FIG. 3 is a circuit block diagram illustrating a configuration of the lighting device according to Embodiment 1; 3 is a graph showing the voltage across the electrolytic capacitor of the power factor correction circuit according to Embodiment 1; 3 is a graph showing a voltage across a capacitor of the buck converter circuit according to the first embodiment. FIG. 6 is a circuit block diagram illustrating a configuration of a lighting device according to Embodiment 2.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a circuit block diagram showing a configuration of a lighting device 10 according to the present embodiment.

  In FIG. 1, the lighting device 10 includes a lighting device 11 (specifically, an LED lighting device) and an LED module 37.

  The lighting device 11 includes a dimming signal interface circuit 14, a control device 15, an output command value generation unit 16, a full-wave rectification circuit 18, a capacitor 19, a power factor correction circuit 12, a buck converter circuit 13, and a diode 35.

  The LED module 37 includes a plurality of LEDs 36 connected in series. The LED 36 is an example of a light source, and is lit by a direct current (predetermined direct current) output from the back converter circuit 13 of the lighting device 11. The LED 36 may be another type of light source such as an organic EL. That is, the LED module 37 may be a module including another type of light source. Further, the number and connection form of LEDs 36 included in the LED module 37 (series, parallel, or a combination of series and parallel) are arbitrary.

  The dimming signal interface circuit 14 receives a dimming control signal transmitted from a dimmer 38 (for example, a controller) outside the lighting device 11.

  The control device 15 (for example, a microcomputer) sets the dimming rate of the LED 36 of the LED module 37 based on the dimming control signal received by the dimming signal interface circuit 14.

  The output command value generation unit 16 generates and outputs an output command signal (a signal indicating an output command value) that commands the dimming rate set by the control device 15.

  The full-wave rectification circuit 18 performs full-wave rectification on the AC voltage applied from the commercial power supply 17 outside the lighting device 11 and outputs a pulsating voltage.

  The capacitor 19 smoothes the pulsating voltage output from the full-wave rectifier circuit 18 and outputs a DC voltage.

  The power factor correction circuit 12 is an example of a step-up chopper circuit, and boosts an input voltage by a switching operation and applies it to the electrolytic capacitor 27. In addition to the electrolytic capacitor 27, the power factor correction circuit 12 includes a coil 20, a MOSFET 21, a control circuit 22, a feedback unit 23, a diode 24, and voltage dividing resistors 25 and 26.

  The coil 20 is an example of an electromagnetic induction element, accumulates energy generated by a current flowing from the capacitor 19 when the MOSFET 21 is on, and releases the energy when the MOSFET 21 is off. The MOSFET 21 is an example of a switching element, and is controlled by the control circuit 22 to perform a switching operation. The diode 24 is an example of a rectifying element, and controls the direction of the direct current generated by the energy released from the coil 20 to the direction of flowing through the electrolytic capacitor 27. The voltage dividing resistors 25 and 26 divide the voltage across the electrolytic capacitor 27. The feedback unit 23 generates and outputs a feedback signal indicating whether or not the voltage across the voltage dividing resistor 26 is higher than a predetermined voltage. The control circuit 22 controls on / off of the MOSFET 21 based on the feedback signal output from the feedback unit 23. Specifically, the control circuit 22 adjusts the on / off frequency and duty ratio of the MOSFET 21 so that the voltage across the electrolytic capacitor 27 becomes a desired voltage (for example, 400 V). Thereby, the DC voltage (input voltage) output from the capacitor 19 is boosted. The electrolytic capacitor 27 smoothes and outputs the boosted DC voltage.

  The buck converter circuit 13 is an example of a lighting circuit. The DC voltage output from the electrolytic capacitor 27 is stepped down by a switching operation to generate a predetermined DC current, and the DC current is output to turn on the LED 36 of the LED module 37. Light up. The buck converter circuit 13 includes a MOSFET 28, a control circuit 29, a feedback unit 30, a diode 31, a coil 32, a capacitor 33, and a current detection resistor 34.

  The MOSFET 28 is an example of a switching element, and is controlled by the control circuit 29 to perform a switching operation with a DC voltage output from the electrolytic capacitor 27 of the power factor correction circuit 12. The coil 32 is an example of an electromagnetic induction element, accumulates energy generated by a current flowing through the MOSFET 28 when the MOSFET 28 is on, and releases the energy when the MOSFET 28 is off. The diode 31 is an example of a rectifying element, and controls the direction of the direct current (predetermined direct current) generated by the energy emitted from the coil 32 to the direction in which the LED 36 of the LED module 37 flows. The capacitor 33 charges the current flowing through the diode 31 and outputs a direct current (predetermined direct current). The direct current output from the capacitor 33 is input to the LED 36 of the LED module 37. The current detection resistor 34 is connected to the low potential side of the LED 36 of the LED module 37. The feedback unit 30 generates and outputs a feedback signal indicating whether or not the voltage across the current detection resistor 34 is higher than a predetermined voltage. The control circuit 29 controls on / off of the MOSFET 28 based on the feedback signal output from the feedback unit 30 and the output command signal output from the output command value generation unit 16. Specifically, the control circuit 29 sets the on / off frequency of the MOSFET 28 so that the voltage across the capacitor 33 becomes a desired voltage, that is, the current flowing through the LED 36 of the LED module 37 becomes a desired current. And adjust the duty ratio.

  The diode 35 is an example of a rectifying unit, and the direction of the current flowing through the MOSFET 28 of the buck converter circuit 13 is changed from the electrolytic capacitor 27 side (the drain terminal side of the MOSFET 28) of the power factor correction circuit 12 to the LED 36 side (the MOSFET 28) of the LED module 37. Control (limit) in one direction to the source terminal side of In the present embodiment, the diode 35 is connected between the electrolytic capacitor 27 of the power factor correction circuit 12 and the MOSFET 28 of the buck converter circuit 13.

  FIG. 2 is a graph showing the voltage across the electrolytic capacitor 27 of the power factor correction circuit 12. FIG. 3 is a graph showing the voltage across the capacitor 33 of the buck converter circuit 13.

  Under normal conditions, the voltage across the electrolytic capacitor 27 of the power factor correction circuit 12 is substantially constant (for example, 400 V) due to the switching operation of the MOSFET 21, as shown in FIG. Similarly, the voltage across the capacitor 33 of the buck converter circuit 13 is substantially constant (for example, 100 to 200 V) by the switching operation of the MOSFET 28 as shown in FIG.

  However, at a low temperature (for example, −40 ° C.), the electrolytic solution inside the electrolytic capacitor 27 is frozen and the capacitance of the electrolytic capacitor 27 is reduced. Therefore, as shown in FIG. Increase. Therefore, if the diode 35 is not connected between the electrolytic capacitor 27 and the MOSFET 28, a reverse voltage is applied to the MOSFET 28 (the potential on the source terminal side of the MOSFET 28 becomes higher than the potential on the drain terminal side), thereby causing the MOSFET 28. As a result, a reverse current flows, causing the MOSFET 28 to fail. In the present embodiment, the diode 35 connected between the electrolytic capacitor 27 and the MOSFET 28 can prevent the reverse current from flowing through the MOSFET 28.

  As described above, according to the present embodiment, even when the lighting device 11 is used at a low temperature of −40 ° C., no reverse current flows through the MOSFET 28 of the buck converter circuit 13, thereby preventing a failure of the MOSFET 28. be able to.

Embodiment 2. FIG.
In the present embodiment, differences from the first embodiment will be mainly described.

  FIG. 4 is a circuit block diagram showing the configuration of the illumination device 10 according to the present embodiment.

  In FIG. 4, the diode 35 is connected to a position different from that in FIG.

  In the present embodiment, the diode 35 is connected between the MOSFET 28 of the buck converter circuit 13 and the connection point of the coil 32 and the diode 31 of the buck converter circuit 13. Thus, as in the first embodiment, the direction of the current flowing through the MOSFET 28 of the buck converter circuit 13 changes from the electrolytic capacitor 27 side (the drain terminal side of the MOSFET 28) of the power factor correction circuit 12 to the LED 36 side (the MOSFET 28) of the LED module 37. To the source terminal side). Therefore, in the present embodiment, the same effect as in the first embodiment can be obtained.

  As mentioned above, although embodiment of this invention was described, you may implement in combination of 2 or more among these embodiment. Alternatively, one of these embodiments may be partially implemented. Alternatively, two or more of these embodiments may be partially combined. In addition, this invention is not limited to these embodiment, A various change is possible as needed.

  DESCRIPTION OF SYMBOLS 10 Illuminating device, 11 Lighting device, 12 Power factor improvement circuit, 13 Buck converter circuit, 14 Dimming signal interface circuit, 15 Control apparatus, 16 Output command value generation part, 17 Commercial power supply, 18 Full wave rectifier circuit, 19 Capacitor, 20 coil, 21 MOSFET, 22 control circuit, 23 feedback unit, 24 diode, 25 voltage dividing resistor, 26 voltage dividing resistor, 27 electrolytic capacitor, 28 MOSFET, 29 control circuit, 30 feedback unit, 31 diode, 32 coil, 33 capacitor , 34 Current detection resistor, 35 Diode, 36 LED, 37 LED module, 38 Dimmer.

Claims (2)

A step-up chopper circuit for stepping up an input voltage by a switching operation, the step-up chopper circuit having an electrolytic capacitor for smoothing the stepped-up input voltage and outputting a DC voltage;
Which is connected in series with the electrolytic capacitor, the switching element performs a switching operation by the DC voltage outputted from the electrolytic capacitor, is connected in series to the series circuit of the electrolytic capacitor and the switching element, the switching element is ON Sometimes it stores energy generated by the current flowing through the switching element, and is connected in parallel to a series circuit of an electromagnetic induction element that releases the energy when the switching element is off, and the electrolytic capacitor and the switching element, A rectifying element that controls a direction of a direct current generated by energy released from the electromagnetic induction element to a direction of flowing to an external light source, and outputs the direct current by a switching operation of the switching element to output the direct current back converter to turn on the A road, to detect the current flowing through the light source, based on the feedback signal detected current and a feedback unit for generating and outputting a feedback signal indicating whether higher than a predetermined current, which is outputted from the feedback unit A buck converter circuit having a control circuit for controlling on / off of the switching element so that the direct current becomes the predetermined current ;
Wherein the said switching elements of the buck converter circuit and the buck converter circuit is connected between the connection point of the inductive element and the rectifying element, the direction of current flowing through the switching elements of the buck converter circuit, the electrolytic capacitor And a diode that controls the light source in one direction from the light source side. A lighting device according to claim 1 ;
A lighting device comprising: a light source that is lit by the direct current output from the buck converter circuit of the lighting device.

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